    Patent literature 1: JP 2008-097413 A
There is known an apparatus that estimates a possibility of collision between vehicles and provides driving assistance. According to a technology described in patent literature 1, for example, a subject vehicle and a different vehicle communicate with each other. The subject vehicle is a host vehicle mounted with a driving assistance apparatus; the different vehicle is also a host vehicle mounted with a driving assistance apparatus. Based on road map information, the technology estimates future estimated vehicle positions of the subject vehicle and the different vehicle each mounted with the driving assistance apparatus. The technology compares the estimated vehicle position of the subject vehicle at a time in the future with the estimated vehicle position of the different vehicle at the time. As a result of the comparison, the estimated vehicle position of the subject vehicle may be near to the estimated vehicle position of the different vehicle. In this case, the technology determines that the subject vehicle is likely to collide with the different vehicle and provides safety support information.
According to the technology in patent literature 1, the subject vehicle needs to always estimate its position on a road represented by the road map information. In addition, the different vehicle (hereinafter referred to as a neighboring vehicle) in the vicinity of the subject vehicle also needs to always estimate its position on a road represented by the road map information. The driving assistance apparatus mounted on the subject vehicle and the driving assistance apparatus mounted on the neighboring vehicle each need to include a map matching function. The technology needs to always perform a map matching process, increasing a calculation load. The driving assistance apparatus mounted on the subject vehicle requires a large amount of calculation if the driving assistance apparatus mounted on the subject vehicle successively acquires the current position of the neighboring vehicle and also determines the current position of the neighboring vehicle by performing the map matching process.
It is an object of the disclosure to provide a driving assistance apparatus that determines whether vehicles highly likely to collide with each other, by using a small amount of calculation in order to perform driving assistance.
To achieve the above object, according to an example of the disclosure, a driving assistance apparatus is provided with a driving assistance section and the following sections. A subject vehicle position determination section is included to successively acquire a position determined by receiving a navigation signal transmitted from a navigation satellite included in a satellite navigation system and successively determine a current position of the vehicle, the vehicle being referred to as a subject vehicle. A subject vehicle estimation section is included to estimate a subject-vehicle estimated trajectory as a subsequent traveling trajectory of the subject vehicle from a current position of the subject vehicle determined by the subject vehicle position determination section and a traveling orientation of the subject vehicle. A neighboring vehicle estimation section is included to estimate a neighboring-vehicle estimated trajectory as a subsequent traveling trajectory of a neighboring vehicle around the subject vehicle by acquiring trajectory estimation information to estimate a neighboring-vehicle estimated trajectory as a subsequent traveling trajectory of the neighboring vehicle via an inter-vehicle communication unit included in the subject vehicle, the trajectory estimation information including a traveling orientation of the neighboring vehicle and a current position of the neighboring vehicle determined based on the navigation signal. An area designation section is included to designate a determination area so as to include a crossing point that is included in the subject-vehicle estimated trajectory and the neighboring-vehicle estimated trajectory. A determination section is included to determine whether the determination area designated by the area designation section includes an intersection node in road map information that represents an intersection of roads as the intersection node. The driving assistance section uses a first driving assistance level when the determination area does not include the intersection node, the first driving assistance level being smaller in driving assistance than a second driving assistance level used when the determination area includes the intersection node.
This configuration estimates the subject-vehicle estimated trajectory as a subsequent traveling trajectory for the subject vehicle and the neighboring-vehicle estimated trajectory as a subsequent traveling trajectory for the neighboring vehicle. The determination area is designated so as to include a crossing point if included in the subject-vehicle estimated trajectory and the neighboring-vehicle estimated trajectory. The determination area is used to determine whether the crossing point is included in an intersection of roads. The determination section determines whether the determination area includes the intersection node.
The subject vehicle and the neighboring vehicle are estimated to pass through the same intersection of roads when the determination area includes the intersection node. The subject vehicle and the neighboring vehicle are estimated not to pass through the same intersection of roads when the determination area does not include the intersection node.
Vehicles typically collide with each other at an intersection of roads. Namely, the subject vehicle and the neighboring vehicle are unlikely to collide when a crossing point is not included in the intersection of roads even if there is a crossing point between the subject-vehicle estimated trajectory and the neighboring-vehicle estimated trajectory. Namely, determining whether the determination area includes an intersection node signifies determining whether the subject vehicle and the neighboring vehicle are likely to collide.
The intersection of roads is highly unlikely to include the crossing point when the determination area contains no intersection node. The subject vehicle and the neighboring vehicle are unlikely to collide when the intersection of roads contains no crossing point. An assistance level determination section uses a driving assistance level to reduce or suppress driving assistance when the determination area includes no intersection node rather than when the determination area includes the intersection node.
The configuration can determine whether a collision is highly likely to occur, by using a small amount of calculation because no map matching process is performed to determine a current position of the neighboring vehicle.